Iron Overload in Horses

I recently wrote an article for The Horse about a study which evaluated the potential link between insulin resistance (IR) and iron overload in horses. Interestingly enough, the study’s purpose was actually to investigate this link in browsing rhinoceroses, but since it’s difficult to get a large group of rhinos together, horses were used as a model. (The two species share a similar digestive tract.)

I have to say I was very excited to come across this study because: A.) I’ve been searching for new studies related to iron overload in horses for a while now, and B.) I have two IR horses, so this particular topic is of special interest to me.

In the study, the researchers mention that the relationship between iron (ferritin) and insulin resistance had not been previously explored in horses. Brian Nielsen, the lead researcher, even said that he’s been surprised by the amount of interest this study has generated (on the horse side of things), and that he and his colleagues may be looking into the issue further. I certainly hope so!

So here’s what I know about iron in the horses’ diet: It’s a trace mineral that is needed by the horse, but it is likely the most oversupplemented mineral in the horse’s diet. I think because iron-related anemia is more common in people, we tend to think it’s a problem for horses as well. But Iron is in nearly everything the horse consumes– grass, hay, dirt, water, most commercial feeds, and the majority of vitamin/ mineral supplements.

Horses only need about 40 ppm of iron to meet their daily requirements, but most equine diets far exceed that amount. For example, my hay analysis for last year showed 162 ppm of iron. (And to think, I once gave my barrel horse Red Cell, a popular iron supplement, at the start of the barrel racing season because he seemed a bit ‘lethargic’ to me. . .) Another point to remember about iron is this: horses have no way to excrete it–it’s stored in their liver and spleen.

Iron deficiency and nutrition-induced anemia are extremely rare in horses and may often be misdiagnosed (as discussed in the article, Horses–Natural Blood Dopers). Horses are much more likely to have problems with too much iron in their diet.

One problem with excess iron is the negative effect it has on the uptake of copper and zinc–two minerals that are often already deficient in horses’ diets–as well as manganese. Dr. Eleanor Kellon recommends an iron: copper: zinc: manganese ratio somewhere between 10:1:3: 3 to 4:1:3:3, with the latter ratio being recommended for IR horses.

The only way to correct this ratio is to add copper and zinc (and maybe manganese, although I’ve never had to do this). Personally, when I began balancing my horses’ trace minerals, I saw a big improvement in their hooves and coats, as evidenced in these before and after photos of my gelding, Bob.

Bob Before

Bob After

Another downside to excess iron in the diet is that it has been linked with predisposition to infection, arthritis, risk of tendon/ ligament problems, as well as altered glucose metabolism (as shown in the study I discussed at the beginning of this post.)

The following are a few easy-to-spot signs of a mineral imbalance in horses (which likely result from too much iron):

bleached or dull coat, mane, and/or tail;

ongoing thrush

brittle or cracking hooves (despite routine hoof care)

poor hoof quality in general

So you may be wondering, what is the answer to dealing with excess iron in the horse’s diet? First of all, try to avoid commercial feeds and supplements with added iron (read the labels before you buy!) Many mineral blocks contain iron as well–I prefer to feed loose plain, white salt.

To correct trace mineral imbalances, either have your pasture and hay tested and work with an equine nutritionist to add deficient minerals individually (or take Dr. Kellon’s NRC Plus course, like I did!), or you can feed a mineral supplement like California Trace that has no added iron.

Another recent blog post on the EasyCare Inc. website discusses iron overload in horses as well–it’s worth the read.

36 Responses

I find this article very interesting. In Oct 2011 I bought a filly and after about 6 weeks I was dumbfounded as to why her coat looked dull and felt rough, no shine at all. After about 4 months I decided to have a mineral analysis done and the analysis showed my mare is sensitive to sugars, she had off the charts levels of other minerals and one was iron. I was advised to never give her red cell, (which I haven’t). Now I read this article that states IR are likely to have high levels of iron. Changing my mares diet to remove all molasses and sugars, has made a big difference in her appearance and attitude. I wish more people and especially Veterinarians would have mineral analysis test run on their horses, takes so much guess work out of feeding.

Yes, there definitely seems to be a link between excess iron in the diet and IR. As far as I’m concerned, no feed or supplement should have added iron as horses likely get plenty of iron from pasture, hay, dirt, and water. Horses rarely seem to suffer from iron-related anemia either. Glad you found the problem with your filly though!

If the iron in the overall diet (including water) is high, it can create a problem with the absorption of zinc and copper. That’s what I would be most concerned about since most horses are already deficient in these two minerals. Might be a good idea to supplement zinc/ copper to bring the trace mineral ratio into balance.

I’m really struggling with grazing over in the uk… for 12 years, grass ad-lib in summer and ad-lib hay with a little hard feed has been enough to keep both my tb and tbx in prime condition, beautiful coats, weight, hooves etc. in the last year or two, they’re having chronic hoof problems on both, though the grass especially. after abscesses in quick succession in both horses, following brittle hooves, the hard-feed started. now the old gelding is becoming stiff and although they both have good coat condition, the mare is stripping weight off the topline fast (stabled due to hoof problems by vets orders) and their hooves are deteriorating. there appears to be a recurrent thrush infection that just won’t clear out on them all, the gelding is still growing out the false sole from last summer’s abscess, the mares feet are so soft the walls are flaring instead of supporting the weight and growing down. It has been particularly warm and wet without the usual freeze here the last couple years and the vet thinks the warm, wet weather along with the subsequent change in the grass nutrients is at fault. I don’t know whether an all-round balancer would be the best approach, or if there is a specific area to try instead of o/d things they may already have in excess as symptoms look similar to excess iron… so far we’re using ‘happy hoof’ along with ‘sixteen plus mix’ seaweed, oil and garlic licks and a similar based maintenance nut, along with ‘biotin plus’ with added zinc….. they’ve been purple-sprayed, tarred, hp’d, kerratex’d, hibiscrubbed and Epsom tubbed, all to no avail and everything has had pleanty trial time, any advise?

We had a horse with all of the discussed issues who foundered last year and had to be put down. I think this would have helped him. I would have also not fed garlic to him…I would have tried Tumeric, with oil and pepper….it is heart breaking to have a horse with an uncontrollable issue. I wish you the best of luck. He was on Prascend for Cushings like issues…I would have switched to Metformin. Best of luck

Hi Vickie–sorry to hear about your horses. I know it can be frustrating. I’m not sure what’s in the supplements you’re using, but I’m guessing they probably don’t have near enough zinc or copper–most supplements don’t. I also wouldn’t feed one if it had any iron at all in it. You can buy zinc and copper individually, but you would just be guessing at how much to feed if you don’t have a hay analysis. The only mineral supplement I know of with plentiful zinc/ copper is California Trace. Not sure if it’s available in the UK though. There is another company that might have a good one and that’s Forage Plus located in Wales.

I would also be concerned with providing the garlic lick (on a continual basis anyways) as too much garlic can cause Heinz body anemia. Also, what type of concentrate and hay are you feeding? That can make a big difference as well. And to me, allowing for plenty of movement is more important than keeping a horse stalled to ‘correct’ hoof problems. . .

thankyou for the replies, after a little re-buffing of feeds we did nock out the garlic and seaweed as the garlic seems to have more cons than pros as far as supplementing for health goes and the seaweed didn’t seem to be making any difference in growth rates… the biotin mix hasn’t been making any difference at all and most feeds have way below maintenance levels in them… along with most things. the 16+ mix seems to have good ratios of vitamins and minerals, though a call to the company will follow tomorrow to find out doses as most bags don’t say how much is in there. I really am struggling to find any sort of balancer without added iron at the minute, its a nightmare! the mare (with the nightmare hooves) has recently been switched onto ‘mare and youngstock’ mix, not ideal but seems to be the only feed with enough copper in it so far… the topline seems better after a week on it, but its obviously a stop-gap atm… i’ll be looking into the suggested feeds in the morning too, i’d really prefer to add as much as possible in single powder form rather than adding who-knows-what to their diets. the mare, unfortunately, had an op on her heel after a light overreach injury on her heel (which again was rubbish condition and underrun) cleaved the side off and is on restricted movement, battling proud flesh which she is naturally prone to. our Fleur seems to be another one of those horses everything happens to… poor thing 🙁 I’m giving it a few weeks before we have bloods done, its false economy carrying on like this. We are just away to get our first order of hay from a different area, we have always been using the meadow hay from next door, i’m guessing any difficiency we have would be in the hay too

Interesting blog, thank you. I have a question for you! Do you think a rusty trough will be contributing to iron overload in my horses? I have one trough that is old and rust spots form on it in spite of regular cleaning. The water does become discoloured but they drink it happily. I’m about to stop using it – just in case.

Hi Linda–Here is a quote from Dr. Kellon, “Usually the forage or water supply does not have to be changed to correct the associated problems. It is the total iron intake that is the problem. That total can be reduced by eliminating supplemental source of iron in the grain-sweet feeds formula and supplements, including phosphorus mineral sources high in iron content.” If you’re at all concerned about the rust, I would go ahead and switch to a different tank though. Definitely wouldn’t hurt.

Iron overload is to a big part due to feeding hay grown on alfisol soil. Alfisol soil is soil with a low pH, which promotes iron absorption into the plants. Seems like Timothy hay is mostly affected. You won’t necessarily see the iron overload in the serum, you have to test the body cell itself, since heavy metals get eliminated from the blood and stored in tissue. I have great results in shifting horses with IR, EMS and even Cushings to a hay lower in iron, detoxing from iron and adding Copper to the diet. US areas with low pH soils seem to have a higher rate of IR horses. We routinely perform a ‘metabolic make-over on these IR horses. Once detoxed, balanced in minerals and on the right calorie-and protein intake, these horses do not have any problems any more.

Casie, as any metal, excess iron is distributed throughout the body and stored everywhere, while some organs have a prevalence to it (brain, endocrine system incl. pancreas) In addition, yes, the liver has a specific task in storing iron for blood building but that is not the iron which overloads the pancreas. As you know the pancreas has two parts, the endocrine and the exocrine part. A publication actually recited by thehorse.com reports the problematic with iron overload and the challenge of the pancreas’ endocrine (insulin issue). There are other issues which I will not bring up here to not complicate the matter further. Yes, the right amount and quality of Zeolites will detox from most heavy metals, including iron. That is not only in the liver, but in all organs. It is state of the art in my program to demonstrate this with cell analysis before and after detox, along with the clinical results. Part of my mission has been to convert “insulin resistant” seeming horses back to a balanced metabolism. I am not saying true insulin resistance does not exist, but it is rare. Here is my view on it: Most horses are in iron overload which drives the copper out of the body. These horses then have cravings for the deficient minerals and overeat, which makes them overweight and throws their blood work off. In addition, iron toxicity leads to laminitis. Endocrinology is a complex matter, highly dependent on nutrition and under-researched in Equidae. To narrow the gap of open questions, Veterinarians, Agriculturists and Nutritionists have to come together instead of tunnel-viewing their discipline.

I have read the article and questions with interest. We currently have a problem with horses legs turning rusty brown and a vet has said its iron staining. Nothing takes the rusty colour out, the field has horses that don’t have the symptoms, it’s only the ones with lots of feathers who get it and I am tearing my hair out wondering what it is and what is causing it as its never happened before

Hi Annie, it’s most likely a cellular iron overload which produces a low iron/copper ratio . I recommend 1) reducing the iron intake if possible. Timothy hay seems to be in particular high in it on alfisol soil. You can pull up a map from the Dept. Of Agriculture to see if your area has alfisol soil. 2) Add a Copper mineral salt. I currently have a case study posted on FB showing a Friesian turning from ‘blonde’ coat color to black within a week taking these measures. FB Gabriele Gross VetMed .

I was surprised to see the problem of iron overload in horses, but can vouch for the effect of too much iron . As I have HH or Hereditary Haemochromatosis, which is genetic disorder that causes iron overload and if undiagnosed, causes all sorts of organ failure/ higher risk of some cancers. As found with horses, iron is not excreted from the body (the exception is woman : child birth, menstruation.) this account for early death in undiagnosed males and females diagnose later in life. First & foremost treatment is by venesection/phlebotomy.

I have a mustang mare that has been having problems with itching, some it is from there flies, but I think it might be something else , I feed her bermuda hay from southern calif, and a mixed hay from colorado ( small amt) could this be from too much iron . also can iron be in the ground and dirt as well. if it is should the eat out of hay bags !!

Hi Terri–It’s possible your horse’s problem is from iron overload, but more likely just an overall mineral imbalance. The trace minerals copper and zinc and play a role in skin allergies as well. I have several blog posts on skin allergies if you’d like to do a search for them.

Just wondering if Natural Iron vs added Iron makes any difference? Found a hanging salt lick from Redmond Rock on a Rope. Doesn’t list Iron; however, when I called they told me that it has “natural” iron that is not a determintal as “added iron”…..your thoughts?

This is a good question, Lisa, and definitely one I’ve thought on some. There are quite a few opinions on this, but personally, I’ve quit worrying about iron when it comes from more natural sources like the ones you’ve mentioned. Dr. Mark DePaulo relayed some good information about this in his comment on this post (which I’ve discussed with him via email) http://blog.easycareinc.com/blog/team-easyboot/got-iron

My horse is currently suffering from excessive iron in his system it has been diagnosed as hemochromatosis. Vet has tried blood letting and steroids but his condition is slowly worsening, and no known cure. Has anyone come across this before? Can anyone offer any alternative ways of treating this?

I have been researching this for our horses also. Our water is really high in Iron.
What peaked my interest is I have Hemochromatosis which is mu body stores iron and does not use it or release it.
With the symptoms I have and looking at the horses I figured it was a huge issue for them.
I had to put my amazing mare down for reasons we couldnt figure out. I spent thousands trying to figure it out 🙁
Thank you for this article but please also check out Hemochromatosis in humans, it will help you understand more!

Hi Carol, so sorry about your mare. I just wrote an article (not yet published) for The Horse on iron overload and hemochromatosis in horses and donkeys. It’s based on this study: https://www.ncbi.nlm.nih.gov/pubmed/30269378. I think researchers are still learning about the effects of chronic iron overload. Hopefully this information will become more readily available very soon though!

About Me

Hi! I'm Casie, a freelance writer specializing in horse health. I'm certified in equine acupressure and have a great interest in equine nutrition and barefoot hoof care. The Naturally Healthy Horse encompasses all of these things, and I would love to have you follow along!

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